Cucumbers can be cultivated either by direct sowing in the designated area or by growing from transplants. Cucumbers are sensitive even to low positive temperatures, so direct sowing can only be done after the risk of late spring frost has passed and once the soil has warmed to a temperature of 17 to 18°C. Under these conditions, seeds germinate in 8 – 10 days; if the temperatures are lower, the germination period is extended, increasing the risk of seed failure due to attacks by saprophytic microorganisms and rodents that feed on the seeds. In continental areas, cucumbers can be sown until mid-July (as a second crop), but this significantly reduces the fruiting period and yield.
Crop Rotation for Cucumbers
Cucumbers do not favor windy locations, so it is advisable to avoid them or plant two to three rows of corn between cucumber rows as a windbreak.
Cucumbers can be grown on the same land only after 3 to 4 years, and the previous crop should not be from the Cucurbitaceae family, nor should it be potatoes, tomatoes (due to the same viruses), brassicas, or corn (due to potential herbicide residue damage). Suitable previous crops include cereals, legumes, onions, lettuce, spinach, kohlrabi, and other vegetables.
Open-Field Cucumber Cultivation
Hand sowing is done in small holes where 3 – 4 seeds are placed. The spacing between the holes in the row is 30 – 60 cm, while the spacing between rows is 100 – 150 cm. The sowing distance depends on the vigor of the cultivar and the sowing time; later sowing uses narrower row and hole spacing. When sowing with a seeder, 10 – 15 viable seeds are sown per meter, achieving a density of 30,000 to 100,000 plants per hectare with a seed usage of 1.2 – 3.5 kg/ha. The direct sowing method is increasingly being replaced by transplanting seedlings grown in containers due to advancements in seedling cultivation technology.
In both cases (direct sowing and transplanting), cucumbers can be grown with support. In smaller gardens, branches can be used as supports, but more commonly, plastic mesh with large openings, 120 cm wide, is used. Supporting the cucumbers allows them to grow vertically, making harvesting easier as most of the fruits are within arm’s reach, and improves pesticide application quality. Most of the above-ground mass does not lie on the ground, providing better air circulation between plants, which reduces the incidence of diseases that thrive in high relative humidity.
Use of Black Polyethylene Mulch
For both cultivation methods, it is recommended to use black polyethylene mulch, which offers multiple benefits. The soil under the black mulch warms up faster, allowing quicker seed germination in direct sowing or faster rooting and growth of transplants. The mulch prevents weed growth, which is especially beneficial as there are no registered herbicides for use in cucumbers in Croatia. Weeds in the inter-row spaces can be easily removed mechanically if cucumbers are grown with support, or a total herbicide can be used, provided the cucumbers are well protected from contact with the herbicide. The advantages of using mulch also include moisture retention and soil structure preservation, as well as keeping the fruits clean from soil.
